Coordination chemistry of silver cations

Area of Science:

• Coordination Chemistry
• Computational Chemistry
• Physical Chemistry

Background:

• Silver cations (Ag+) typically show tetrahedral coordination in pure solvents.
• In the presence of ligands like ammonia, Ag+ forms linear complexes, often attributed to sd-hybridization.
• Understanding the factors governing Ag+ coordination in mixed solvent systems is crucial.

Purpose of the Study:

• To investigate the ligand exchange reactions of ammoniated silver cations with water.
• To explore the complementary reaction of hydrated silver cations with ammonia.
• To elucidate the factors controlling silver cation coordination in mixed solvent clusters.

Main Methods:

• Fourier Transform Ion Cyclotron Resonance (FT-ICR) mass spectrometry was employed to study cluster reactions.
• Density Functional Theory (DFT) calculations were performed to complement experimental findings.
• Investigated reactions of Ag+(NH3)n (n=11-23) with H2O and Ag+(H2O)n (n=25-45) with NH3.

Main Results:

• Ligand exchange reactions lead to clusters with a limited number of ammonia ligands.
• Ammoniated silver clusters rapidly lose ligands until two or three NH3 remain, with slower loss of an additional ligand.
• Hydrated silver clusters rapidly uptake up to five ammonia ligands, with inefficient uptake of a sixth.

Conclusions:

• A delicate balance of competing effects governs silver cation coordination.
• Key factors include Ag+ preference for sd-hybridization, its polarization of ligands affecting hydrogen bonding, and solvent network formation.
• These factors collectively explain the observed coordination disparities in mixed solvent systems.